1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/io.h> 3 #include <linux/slab.h> 4 #include <linux/memblock.h> 5 #include <linux/mem_encrypt.h> 6 #include <linux/pgtable.h> 7 8 #include <asm/set_memory.h> 9 #include <asm/realmode.h> 10 #include <asm/tlbflush.h> 11 #include <asm/crash.h> 12 13 struct real_mode_header *real_mode_header; 14 u32 *trampoline_cr4_features; 15 16 /* Hold the pgd entry used on booting additional CPUs */ 17 pgd_t trampoline_pgd_entry; 18 19 void __init reserve_real_mode(void) 20 { 21 phys_addr_t mem; 22 size_t size = real_mode_size_needed(); 23 24 if (!size) 25 return; 26 27 WARN_ON(slab_is_available()); 28 29 /* Has to be under 1M so we can execute real-mode AP code. */ 30 mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE); 31 if (!mem) { 32 pr_info("No sub-1M memory is available for the trampoline\n"); 33 return; 34 } 35 36 memblock_reserve(mem, size); 37 set_real_mode_mem(mem); 38 crash_reserve_low_1M(); 39 } 40 41 static void __init setup_real_mode(void) 42 { 43 u16 real_mode_seg; 44 const u32 *rel; 45 u32 count; 46 unsigned char *base; 47 unsigned long phys_base; 48 struct trampoline_header *trampoline_header; 49 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 50 #ifdef CONFIG_X86_64 51 u64 *trampoline_pgd; 52 u64 efer; 53 #endif 54 55 base = (unsigned char *)real_mode_header; 56 57 /* 58 * If SME is active, the trampoline area will need to be in 59 * decrypted memory in order to bring up other processors 60 * successfully. This is not needed for SEV. 61 */ 62 if (sme_active()) 63 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT); 64 65 memcpy(base, real_mode_blob, size); 66 67 phys_base = __pa(base); 68 real_mode_seg = phys_base >> 4; 69 70 rel = (u32 *) real_mode_relocs; 71 72 /* 16-bit segment relocations. */ 73 count = *rel++; 74 while (count--) { 75 u16 *seg = (u16 *) (base + *rel++); 76 *seg = real_mode_seg; 77 } 78 79 /* 32-bit linear relocations. */ 80 count = *rel++; 81 while (count--) { 82 u32 *ptr = (u32 *) (base + *rel++); 83 *ptr += phys_base; 84 } 85 86 /* Must be perfomed *after* relocation. */ 87 trampoline_header = (struct trampoline_header *) 88 __va(real_mode_header->trampoline_header); 89 90 #ifdef CONFIG_X86_32 91 trampoline_header->start = __pa_symbol(startup_32_smp); 92 trampoline_header->gdt_limit = __BOOT_DS + 7; 93 trampoline_header->gdt_base = __pa_symbol(boot_gdt); 94 #else 95 /* 96 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR 97 * so we need to mask it out. 98 */ 99 rdmsrl(MSR_EFER, efer); 100 trampoline_header->efer = efer & ~EFER_LMA; 101 102 trampoline_header->start = (u64) secondary_startup_64; 103 trampoline_cr4_features = &trampoline_header->cr4; 104 *trampoline_cr4_features = mmu_cr4_features; 105 106 trampoline_header->flags = 0; 107 if (sme_active()) 108 trampoline_header->flags |= TH_FLAGS_SME_ACTIVE; 109 110 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd); 111 trampoline_pgd[0] = trampoline_pgd_entry.pgd; 112 trampoline_pgd[511] = init_top_pgt[511].pgd; 113 #endif 114 } 115 116 /* 117 * reserve_real_mode() gets called very early, to guarantee the 118 * availability of low memory. This is before the proper kernel page 119 * tables are set up, so we cannot set page permissions in that 120 * function. Also trampoline code will be executed by APs so we 121 * need to mark it executable at do_pre_smp_initcalls() at least, 122 * thus run it as a early_initcall(). 123 */ 124 static void __init set_real_mode_permissions(void) 125 { 126 unsigned char *base = (unsigned char *) real_mode_header; 127 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 128 129 size_t ro_size = 130 PAGE_ALIGN(real_mode_header->ro_end) - 131 __pa(base); 132 133 size_t text_size = 134 PAGE_ALIGN(real_mode_header->ro_end) - 135 real_mode_header->text_start; 136 137 unsigned long text_start = 138 (unsigned long) __va(real_mode_header->text_start); 139 140 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT); 141 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT); 142 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT); 143 } 144 145 static int __init init_real_mode(void) 146 { 147 if (!real_mode_header) 148 panic("Real mode trampoline was not allocated"); 149 150 setup_real_mode(); 151 set_real_mode_permissions(); 152 153 return 0; 154 } 155 early_initcall(init_real_mode); 156